1. Field of the Invention
The invention relates to an instrument for cutting and otherwise shaping donor bone for custom fit as spacer implants for spinal fusions in the human spine as a replacement for one or more intervertebral discs in the cervical, thoracic or lumbar spines.
2. Discussion of the Prior Art
When intervertebral discs in the lumbar of humans become injured, degenerated, or diseased, a preferred treatment is to remove the damaged disc and implant in its place a spacer customly constructed from donor bone to facilitate bony fusion by bone growth between adjacent vertebra. Typically the damaged intervertebral disc is removed and bone graft material is packed in the intervertebral space. Such spinal fusions are becoming evermore commonly preformed and the trend is for the procedure to become more complicated involving more and more instrumentation and implants of various sorts and sizes to aide in the fusion construct. Spacer implants are pre-manufactured from donor bone and come in an extremely large variety of shapes and sizes and they are designed according to the vendor's philosophy, not the doctor's philosophy, regarding how the particular implant aides in the construct and fusion process. In addition, these pre-manufactured implants are becoming extremely expensive.
These pre-machined spacer implants are machined by the surgical supply vendors to exact dimensions and packaged according to size of the implant. At the time of surgery, the physician determines the size of the implant required to adequately fill the space to be fused, and a pair of appropriately sized implants are selected and opened. As a present day example, a one level lumbar fusion, utilizing posterior lumbar inter-body fusion implants (PLIF) costs approximately $4,000.00 U.S. Dollars for the PLIF implants alone. For each additional level which is fused, this cost is multiplied. For example a two level fusion implant costs $8,000.00. Over the last decade, greater financial restraints have been placed on hospitals, and subsequently on physicians performing these procedures and surgical implant vendors for lower cost options. Presently no such options are available. In addition, the surgeon has no input or choice in selecting the particular design of the spacer implant to provide a good custom fit.
Recently there has also been pressure to produce biologically conductive PLIF bony implants since the body will eventually assimilate the PLIF material and the PLIF implant does not interfere with follow-up radiographs as do metal implants. The implants need to be formed with exact precision and be exactly reproducible so that there will exist a well formed pair of PLIF implants. It is therefore an object of the present invention to permit the surgeon, himself or herself, to fabricate such donor bone implants quickly within the operating room to exact custom dimensions while the operative case is ongoing.